Reef Pi - Kalk overdose control using PH value - unsure of exact values to fill

[Koleswrath]

Hello, I'm having a bit of trouble figuring out what values to input to Reef Pi to ensure my Kamoer doser doesn't stay on and nuke my tank with Kalk. Can one of you Reef Pi experts help out a layman please. @robsworld78, @Ranjib
Thanks!!

This is where I'm at right now. I've got the doser setup as equipment but I'm not sure how the upper and lower function correspond to the upper and lower threshold.

 

[Reefing Madness]

 

[Sral]

pH tab control and temperature seem to use the same code, which also makes sense from a logical standpoint:

- the upper function is triggered on crossing the Lower Threshold, e.g. for temperature the heater turns on and will be disabled when the value is higher than Lower Threshold + Hysteresis again.

- the lower function is consequently triggered on crossing the Upper Threshold, e.g. for temperature the chiller turns on and will be disabled when the value is lower than Upper Threshold - Hysteresis again

That way the value is kept between the Lower and Upper Threshold, but the equipment doesn't jitter around the Thresholds, due to the hysteresis. Lower Threshold must be lower than the upper threshold and hysteresis must be smaller than the distance between the thresholds.

Now for kalkwasser dosing I think there might be a few important things to consider:
- How quickly does your doser pump and how concentrated is the solution ?
- How quickly does the change in pH due to kalkwasser dosing arive at your pH meter ?

My concern would be that you might dump too much Kalkwasser before the pH meter registers a significant change and then you have dumped so much, that your pH rises by way too much and there is no way of stopping it.

I can't speak from experience, but my way of testing would be:
- Note down the current time
- Activate the doser manually for an amount X that you feel safe with
- Turn the doser of and watch the reaction in pH vs time

If pH rises significantly but very delayed, you have a problem and might need to reconsider where you place your pH meter and dosing outlets. You could also try reducing pump speed and/or Kalkwasser concentration.
If pH doesn't rise at all after maybe 2-5 minutes, repeat with a longer time span until you see an increase in pH that you would like to see in reality. Note down the dosing time, the increase in pH and the amount of time after dosing that it took for that rise in pH to completely register and finish rising.

If you would like, I could try to look around and try calculating the rise in pH you could expect from the speed of your dosing pumps, the concentration of Kalkwasser and the volume of water in your system. If you have enough experience, you can judge that yourself of course ^^

 

[Koleswrath]

- the upper function is triggered on crossing the Lower Threshold, e.g. for temperature the heater turns on and will be disabled when the value is higher than Lower Threshold + Hysteresis again.

- the lower function is consequently triggered on crossing the Upper Threshold, e.g. for temperature the chiller turns on and will be disabled when the value is lower than Upper Threshold - Hysteresis again

Hi Sral, thanks for helping me out!
The way I'm understanding this is that both functions are based on turning equipment on when a threshold is reached and it will turn off after the sensor hits the hysteresis value.
In my case the equipment is already on a timer to set a consistent dose every hour. All I want to do is have a safety backup in place in case the timer malfunctions at the pump sticks on.

You bring up some good points about the speed at which PH rises and how much Kalk might get added before I hit the upper limit to shut down the pump. My PH probe is in the first section of my sump and I dose Kalk to the last section so it could take quite awhile. I do have a ton of system flow through my sump though so that is in my favor.
Since I'm not looking to control the doser with PH values and only looking for emergency shutdown I think it would still be useful to limit the amount of Kalk that could be added if a dosing pump got stuck on. My Kalk reservoir holds 3 gallons and my system volume is 17 gallons so it would be disastrous if the pump got stuck and dumped it all.
Can you think of a way this could be done by entering certain values in the above fields?

 

[Sral]

Hi Sral, thanks for helping me out!
The way I'm understanding this is that both functions are based on turning equipment on when a threshold is reached and it will turn off after the sensor hits the hysteresis value.
In my case the equipment is already on a timer to set a consistent dose every hour. All I want to do is have a safety backup in place in case the timer malfunctions at the pump sticks on.

You bring up some good points about the speed at which PH rises and how much Kalk might get added before I hit the upper limit to shut down the pump. My PH probe is in the first section of my sump and I dose Kalk to the last section so it could take quite awhile. I do have a ton of system flow through my sump though so that is in my favor.
Since I'm not looking to control the doser with PH values and only looking for emergency shutdown I think it would still be useful to limit the amount of Kalk that could be added if a dosing pump got stuck on. My Kalk reservoir holds 3 gallons and my system volume is 17 gallons so it would be disastrous if the pump got stuck and dumped it all.
Can you think of a way this could be done by entering certain values in the above fields?

Yes, that would be correct. You can trick it though: you can try to create a second Outlet on the doser pin, but reverse it relative to normal operation. That way, every time this Inverted Outlet gets "activated", it actually turns off the pump.
Problem might be that this would effectively turn the doser on permanently when pH drops below hysteresis again ... unless your lower Threshold is -20 and your hysteresis absurdly high at 27. This way after reaching the "upper threshold" it should realistically never turn the pump back on. That might make it slightly difficult to get the system to reset after it has actually run into this emergency, so keep that in mind. Restarting the pH entry or ReefPi completely might work in that situation.

I'm not fully sure how the system will behave though. My current understanding is that the timer will run at some point and turn on the dosing pump, irrespective of pH. Next time the pH value gets measured it notices that the pH is still over and should turn the pump back off again through the Reversed Outlet. Not sure though if the logic in that system doesn't get stuck thinking it already activated the "pH lowering Equipment".

I'd definitely test how it behaves by setting an "upper threshold" so low that it gets triggered on the next measurement period and watch what the system does at the next timer.

 

[Koleswrath]

That might make it slightly difficult to get the system to reset after it has actually run into this emergency, so keep that in mind. Restarting the pH entry or ReefPi completely might work in that situation.

Thanks again, really appreciate it.
I feel like I need to keep things simple with Reef Pi or I'll seriously screw something up so I might just use the Reef Pi timers to power up the dosing up 1 minute before the dosing pump internal timer comes one and shut it off 1 minute after the dosing pump is set to turn off.
Hopefully powering up and down 24 times a day doesn't wreck my programmable dosing pump.

I'm surprised this hasn't come up more...using PH as a failsafe for Kalkwasser dosing seems to be a common thing to do on the Apex.

 

[Sral]

Thanks again, really appreciate it.
I feel like I need to keep things simple with Reef Pi or I'll seriously screw something up so I might just use the Reef Pi timers to power up the dosing up 1 minute before the dosing pump internal timer comes one and shut it off 1 minute after the dosing pump is set to turn off.
Hopefully powering up and down 24 times a day doesn't wreck my programmable dosing pump.

I'm surprised this hasn't come up more...using PH as a failsafe for Kalkwasser dosing seems to be a common thing to do on the Apex.

I remember somebody doing something like this … I think he tried dosing with timers and turned that timer on and off with the pH tab. Might had to use a macro for that, iirc

 

[Sral]

Here you go:

Doser Configuration Question

Hi Guys, I've been directly my questions to Rob so far since I'm using his hardware, but thought I'd toss this question out to the group... I’m currently dosing kalk using a 12v dosing pump defined as ‘equipment’ with the equipment tied to a ‘minute’ timer that turns the pump on for 2 seconds...

www.reef2reef.com

 

[Sral]

He did use a macro to run the doser directly for 2 seconds every time pH measurement is below threshold.